Virtually all devices that consume liquid fuel include a fuel filter. The most common example of a liquid fuel filter is that used on automobile and truck engines. Fuel filters have always been important as a part of internal combustion engines since any dirt or contamination in fuel can easily cause carburetor problems or, in newer engines, fuel injector problems. Most manufacturers of internal combustion engines recommend periodic replacement of fuel filters to make certain that they do not become clogged and impair engine performance and to be certain that filtration of the fuel is effective to remove solids and other contaminants.
When fuel filters were first marketed for internal combustion engines, they were typically in the form of a permanently mounted housing that could be disassembled and the filter element itself being replaced. In recent years, substantially all manufacturers of internal combustion engines, and particularly manufacturers of cars and trucks, employ disposable filters in which the housings that contain the filter elements are integral and are not subject to being disassembled. That is, when it is necessary to replace a fuel filter, the entire filter housing is thrown away.
A problem that has long been known to the designers of fuel systems for automobile and truck engines is that fuel flowing through a filter can result in the accumulation of static electricity. As fuel passes through a filter media, the flowing fuel is stripped of electrons with the electrons collecting on the inside of the filter housing. If the fuel filter housing is metal, this electrical charge is readily conducted away, but when the housing is made of a non-conductive material, such as plastic, the charge is not readily conducted away and thus a buildup of electrostatic charge can occur to the point where a static discharge can take place. When an electrostatic charge builds up in a filter that exceeds the dielectric strength of the material of which the filter body is formed, a discharge can occur between the filter housing and an adjacent conductive part of the engine with which the filter is employed. Discharge through a plastic filter housing can cause a pinhole in the housing and leakage of fuel can occur.